Petroleum Products_Refinery Basics_chemical engineering.pdf

PETROLEUM ELECTIVE REFINERY BASIS. there are different kind of refinery basis basic description on those

1. Petroleum Products: Refinery
Basics
Quality Controls and Market Standards
By-
Aniruddha Sanyal
Assistant Professor
Department of Chemical Engineering
National Institute of Technology Calicut
Kozhikode 673601, Kerala, India.

2. Refinery Basics
•A small refinery will take in 2k to 10k tons of crude oil/day.
•A large refinery will take 20k to 40k tons of crude oil/day, and there
are few refineries which can reach up to 60k tons of crude oil/ day.
•Refineries vary in complexity; i.e. in the variety of processes operated
and of products that are send out.
•Simple refinery may make only gasoline, diesel fuel and heavy fuel. In
such cases units like distilling unit, sweeteners and reformers will be
present.
•The complex refineries have desulfurizers in addition.

3. Objectives in Refining

4. Typical Petroleum
Refinery Flow Diagram

5. Main Processing Units
•CrudeOilDistillationunit:
Distillstheincomingcrudeoilintovariousfractionsforfurtherprocessingin
otherunits.
•Vacuumdistillationunit:
Furtherdistillstheresidueoilfromthebottomofthecrudeoildistillation
unit.Thevacuumdistillationisperformedatapressurewellbelow
atmosphericpressure.
•Naphthahydrotreaterunit:
Useshydrogentodesulfurizethenaphthafractionfromthecrudeoil
distillationorotherunitswithintherefinery.
•Catalyticreformingunit:
Convertsthedesulfurizednaphthamoleculesintohigher-octanemolecules
toproducereformate,whichisacomponentoftheend-productgasolineor
petrol.

6. Main Processing Units
•Alkylationunit:
Convertsisobutaneandbutylenesintoalkylate,whichisaveryhigh-
octanecomponentoftheend-productgasolineorpetrol.
•Isomerizationunit:
Convertslinearmoleculessuchasnormalpentaneintohigher-octane
branchedmoleculesforblendingintotheend-productgasoline.Also
usedtoconvertlinearnormalbutaneintoisobutaneforuseinthe
alkylationunit.
•Distillatehydrotreaterunit:
Useshydrogentodesulfurizesomeoftheotherdistilledfractionsfrom
thecrudeoildistillationunit(suchasdieseloil).
•Merox(mercaptanoxidizer)orsimilarunits:
DesulfurizeLPG,keroseneorjetfuelbyoxidizing
undesiredmercaptanstoorganicdi-sulfides.

7. Main Processing Units
•Aminegastreater,Clausunit,andtailgastreatment:
Forconvertinghydrogensulfidegasfromthehydrotreatersintoend-
productelementalsulfur.Thelargemajorityofthe64,000,000metric
tonsofsulfurproducedworldwidein2005wasbyproductsulfurfrom
petroleumrefiningandnaturalgasprocessingplants.
•Fluidcatalyticcracking(FCC)unit:
Upgradestheheavier,higher-boilingfractionsfromthecrudeoil
distillationbyconvertingthemintolighterandlowerboiling,more
valuableproducts.
•Hydrocrackerunit:
Useshydrogentoupgradeheavierfractionsfromthecrudeoil
distillationandthevacuumdistillationunitsintolighter,morevaluable
products.

8. Main Processing Units
•Visbreakerunit:
Itupgradesheavyresidualoilsfromthevacuumdistillationunitby
thermallycrackingthemintolighter,morevaluablereducedviscosity
products.
•Delayedcokingandfluidcokerunits:
Convertveryheavyresidualoilsintoend-productpetroleumcokeas
wellasnaphthaandpetroloilby-products.

9. Auxiliary Processing Units: Pretreatments
•Steamreformingunit:Convertsnaturalgasintohydrogenforthe
hydrotreatersand/orthehydrocracker.
•Sourwaterstripperunit:Usessteamtoremovehydrogensulfidegas
fromvariouswastewaterstreamsforsubsequentconversionintoend-
productsulfurintheClausunit.
•Utilityunitssuchascoolingtowersforfurnishingcirculatingcooling
water,steamgenerators,instrumentairsystemsforpneumatically
operatedcontrolvalvesandanelectricalsubstation.
•Desalting:Typicallycontains10–200PTB(poundsperthousand
barrelsofoil),whichareremovedusingsettlingwith/without
electricalmeans.Thecrudemaystillcontain2-4PTBsalts.

10. Pretreatments-contd.
•WastewatercollectionandtreatingsystemsconsistingofAPI
separators,dissolvedairflotation(DAF)unitsandsometypeof
furthertreatment(suchasanactivatedsludgebiotreater)tomake
thewastewaterssuitableforreuseorfordisposal.
•Liquifiedgas(LPG)storagevesselsforpropaneandsimilargaseous
fuelsatapressuresufficienttomaintaintheminliquidform.These
areusuallysphericalvesselsorbullets(horizontalvesselswith
roundedends).
•Storagetanksforcrudeoilandfinishedproducts,usuallyvertical,
cylindricalvesselswithsomesortofvapouremissioncontroland
surroundedbyanearthenbermtocontainliquidspills.

11. Types of Impurities in Crude Oil:
which needs to be removed
•Oleophobic
❖Salts-mainly chlorides and sulphates of Na, Ca, Mg
❖Sediments-such as silt, sand, drilling mud, iron oxide, iron sulphide
❖Water –presents as soluble, emulsified and/or finely dispersed water
•Oleophilic
❖Sulphur compounds
❖Organometallic compounds containing Ni, V, Fe, As.
❖Naphthenic acids
❖Nitrogen compounds

12. Problems that may be caused by the impurities:
•Corrosion in the atmospheric distillation overhead system caused by HCl,
which is liberated due to hydrolysis/dissociation of chloride salts
•Increased consumption of ammonia to neutralize the HCl
•Erosion of crude oil pumps, pipelines and valves by suspended matter
through abrasive action
•Plugging of equipment and fouling of heat-transfer surfaces
•Product degradation, like high ash content in fuel oil
•Trace metals in distillates, which act as catalyst poisons

13. Test methods for determination of corrosive
properties in crude oil
•Total Sulphur
Inorganic Sulphur creates corrosion, and hence a refiners needs to
know its initial composition.
(Lamp method for volatile petroleum products or Bomb Method IS
1448:1991 for heavy petroleum products).
Sulphur in the sample is oxidized by combustion, and it is estimated
volumetrically after absorption in hydrogen peroxide or by gravimetric
methods after converting into barium sulphate.

14. Test methods for determination of corrosive
properties in crude oil
•Acidity and Alkalinity
New and used petroleum products may contain acidic constituents
present as additives or as degradation products, such as oxidation
products, formed during service.
Total acidity is the sum of organicand inorganicacidity.
Acids in the sample are extracted using neutral alcohol and then
titrated against KOH under hot conditions.
Inorganic acidity accounts for mineral acid present in the sample.

15. Test methods for determination of corrosive
properties in crude oil
•Copper-strip Corrosion Test
Thistestservesasameasureof
possibledifficultieswithCu,Brass,or
Bronzepartsofthefuelsystems.
AcleanandsmoothlypolishedCustrip
isimmersedinthesampleatspecific
temperatureforacertaintime.The
stripisthenremoved,washedwith
aromaticandSulphur-freepetroleum
spirit;andexaminedforcorrosion
standardcolorcode.
Indicates presence of
Sulphur compounds

16. Flash Point and Fire Point
Flashpointisthelowesttemperatureatwhichapplicationoftestflame
causesthevapourabovetheoiltoignite.
Firepointisthelowesttemperatureatwhichtheoilignitesand
continuestoburnfor5second.
•Abel Apparatus
•Pensky-Martens Apparatus (19℃-49℃)
•Cleveland Apparatus (>79℃)

17. Octane Number
•Itcheckstheanti-knockingqualityofthegasoline(petrolormotorspirit).
•Theknockingofmotorfuelsiscomparedwiththeblendsofreferencefuels.
•Itisthevolumepercentageofiso-octaneinablendwithn-heptanewhichis
equaltothetestfuelinknockintensityunderstandardizedandcloselycontrolled
conditionsoftestina“single-cylinder,variablecompressionratio”engines.
•Two octane tests can be performed for gasoline.
•The motor octane number (MON) indicates engine performance at highway
conditions with high speeds (900rpm). On the other hand, the research octane
number (RON) is indicative of low-speed city driving (600rpm).
•Pure n –heptane is assigned a value of zero octane while isooctane is assigned
100 octane. Hence, an 80vol% isooctane mixture has an octane number of 80.

18. Ignition quality of Diesel/Kerosene
•Cetane Number
•Diesel Index
•Aniline Point

19. Properties of Different Crude Oil Fractions